Selective catalytical dehydrochlorination of hydrochlorofluorocarbons

ABSTRACT

A dehydrochlorination process is disclosed. The process involves contacting R f CHClCH 2 Cl with a catalyst in a reaction zone to produce a product mixture comprising R f CCl═CH 2 , wherein said catalyst comprises MY supported on carbon, and wherein R f  is a perfluorinated alkyl group, M=K, Na or Cs, and Y=F, Cl or Br.

BACKGROUND

1. Field of the Disclosure

This disclosure relates in general to the selective catalyticdehydrochlorination of hydrochlorofluorocarbons (HCFCs) to makehydrochlorofluoroolefins (HCFOs). More specifically, the catalysts arealkali metal compounds supported on carbon.

2. Description of Related Art

Hydrochlorofluoroolefins (HCFOs), having low ozone depletion potentialand low global warming potentials, are regarded as candidates forreplacing saturated CFCs (chlorofluorocarbons) and HCFCs(hydrochlorofluorocarbons). HCFOs can be employed in a wide range ofapplications, including their use as refrigerants, solvents, foamexpansion agents, cleaning agents, aerosol propellants, dielectrics,fire extinguishants and power cycle working fluids. For example,HCFO-1233xf (CF₃CCl═CH₂) can be used as a foam expansion agent, fireextinguishant, refrigerant, et al. HCFO-1233xf is also an intermediatein the production of 2,3,3,3-tetrafluoropropene (HFO-1234yf) which is arefrigerant with zero ozone depletion potential and low global warmingpotential.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure provides a dehydrochlorination process. Theprocess comprises contacting R_(f)CHClCH₂Cl with a catalyst in areaction zone to produce a product mixture comprising R_(f)CCl=CH₂,wherein said catalyst comprises MY supported on carbon, and whereinR_(f) is a perfluorinated alkyl group, M=K, Na or Cs, and Y=F, Cl or Br.

DETAILED DESCRIPTION

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as defined in the appended claims. Other features andbenefits of any one or more of the embodiments will be apparent from thefollowing detailed description, and from the claims.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the present invention, suitablemethods and materials are described below. All publications, patentapplications, patents, and other references mentioned herein areincorporated by reference in their entirety, unless a particular passageis cited. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

When an amount, concentration, or other value or parameter is given aseither a range, preferred range or a list of upper preferable valuesand/or lower preferable values, this is to be understood as specificallydisclosing all ranges formed from any pair of any upper range limit orpreferred value and any lower range limit or preferred value, regardlessof whether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range.

The term “dehydrochlorination”, as used herein, means a process duringwhich hydrogen and chlorine on adjacent carbons in a molecule areremoved.

The term “hydrochlorofluoroolefin”, as used herein, means a moleculecontaining hydrogen, carbon, fluorine, chlorine, and at least onecarbon-carbon double bond. Exemplary hydrochlorofluoroolefins in thisdisclosure include HCFO-1233xf.

The term “alkyl”, as used herein, either alone or in compound words suchas “perfluorinated alkyl group”, includes cyclic or acyclic andstraight-chain or branched alkyl groups, such as, methyl, ethyl,n-propyl, i-propyl, or the different isomers thereof.

The term “perfluorinated alkyl group”, as used herein, means an alkylgroup wherein all hydrogens on carbon atoms have been substituted byfluorines. Examples of a perfluorinated alkyl group include —CF₃ and—CF₂CF₃.

The term “product selectivity to R_(f)CCl═CH₂”, as used herein, meansthe molar percentage of R_(f)CCl═CH₂ obtained in the process compared tothe total molar amounts of all products obtained.

The term “dehydrochlorination selectivity to R_(f)CCl═CH₂”, as usedherein, means the molar percentage of R_(f)CCl═CH₂ based on the totalmolar amount of R_(f)CCl═CH₂ and R_(f)CH═CHCl obtained in thedehydrochlorination reaction of R_(f)CHClCH₂Cl.

The term “an elevated temperature”, as used herein, means a temperaturehigher than the room temperature.

Disclosed is a dehydrochlorination process comprising contactingR_(f)CHClCH₂Cl with a catalyst in a reaction zone to produce a productmixture comprising R_(f)CCl═CH₂, wherein said catalyst comprises MYsupported on carbon, and wherein R_(f) is a perfluorinated alkyl group,M=K, Na or Cs, and Y=F, Cl or Br.

In some embodiments of this invention, R_(f) is —CF₃ or —CF₂CF₃. In someembodiments of this invention, R_(f)CHClCH₂Cl is CF₃CHClCH₂Cl(HCFC-243db), and R_(f)CCl═CH₂ is CF₃CCl═CH₂ (HCFO-1233xf).

Some hydrochlorofluoroolefins of this disclosure, e.g., CF₃CH═CHCl(HCFO-1233zd), exist as different configurational isomers orstereoisomers. When the specific isomer is not designated, the presentdisclosure is intended to include all single configurational isomers,single stereoisomers, or any combination thereof. For instance,HCFO-1233zd is meant to represent the E-isomer, Z-isomer, or anycombination or mixture of both isomers in any ratio.

The starting materials for the dehydrochlorination processes in thisdisclosure, i.e., R_(f)CHClCH₂Cl, can be synthesized by methods known inthe art. For example, HCFC-243db may be prepared by chlorinatingCF₃CH═CH₂ or by the addition reaction of CF₂═CHCl with CFClH₂.

The dehydrochlorination process can be carried out in liquid phase orvapor phase using well-known chemical engineering practice, whichincludes continuous, semi-continuous or batch operations. Thetemperature in the reaction zone is typically from about 140° C. toabout 400° C. In some embodiments of this invention, the temperature inthe reaction zone is from about 150° C. to about 250° C. In someembodiments of this invention, the temperature in the reaction zone isfrom about 175° C. to about 225° C. The dehydrochlorination process canbe conducted at superatmospheric, atmospheric, or subatmosphericpressures. The contact time of the starting material R_(f)CHClCH₂Cl withthe catalyst can be largely varied. Typically, the contact time is fromabout 10 seconds to about 150 seconds. In some embodiments of thisinvention, the contact time is from about 40 seconds to about 100seconds. The contacting step of this invention may be carried out bymethods known in the art. In some embodiments of this invention,starting material R_(f)CHClCH₂Cl, optionally with an inert gas, is fedto a reactor containing the catalyst. In some embodiments of thisinvention, starting material R_(f)CHClCH₂Cl, optionally with an inertgas, is passed through the catalyst bed in a reactor. In someembodiments of this invention, starting material

R_(f)CHClCH₂Cl, optionally together with an inert gas, may be mixed withthe catalyst in a reactor with stir or agitation.

The dehydrochlorination process may be conducted in the presence of aninert gas such as He, Ar, or N₂. In some embodiments of this invention,the inert gas is co-fed into the reactor with the starting material.

In accordance with this invention, catalysts suitable fordehydrochlorination are provided. Said catalysts comprise carbonsupported alkali metal halide salt represented by the formula MY,wherein M=K, Na or Cs, and Y=F, Cl or Br. In some embodiments of thisinvention, MY is KF. In some embodiments of this invention, MY is KCl.

The alkali metal halide salt can be deposited on the carbon supportusing deposit techniques well known in the art. For example, alkalimetal halide salt can be dissolved in deionized water and then mixedwith freshly dried acid washed activated carbon. The mixture can begently stirred until the solution of the alkali metal halide salt iscompletely absorbed by the activated carbon. Finally, the loadedactivated carbon is dried at an elevated temperature and stored in asealed container for use as a catalyst. In some embodiments of thisinvention, the catalyst contains from about 5 wt % (weight percent) toabout 40 wt % alkali metal halide salt based on the total amount ofalkali metal halide salt and carbon. In some embodiments of thisinvention, the catalyst contains from about 10 wt % to about 30 wt %alkali metal halide salt based on the total amount of alkali metalhalide salt and carbon.

Carbon used in the embodiments of this invention may come from any ofthe following sources: wood, peat, coal, coconut shells, bones, lignite,petroleum-based residues and sugar. Commercially available carbons whichmay be used include those sold under the following trademarks: Barneby &Sutcliffe™, Darco™, Nucharm, Columbia JXN™ Columbia LCK™, Calgon™ PCB,Calgon™ BPL, Westvaco™, Norit™, Takeda™ and Barnaby Cheny NB™ The carbonalso includes three dimensional matrix porous carbonaceous materials.Examples are those described in U.S. Pat. No. 4,978,649. In oneembodiment of the invention, carbon includes three dimensional matrixcarbonaceous materials which are obtained by introducing gaseous orvaporous carbon-containing compounds (e.g., hydrocarbons) into a mass ofgranules of a carbonaceous material (e.g., carbon black); decomposingthe carbon-containing compounds to deposit carbon on the surface of thegranules; and treating the resulting material with an activator gascomprising steam to provide a porous carbonaceous material. Acarbon-carbon composite material is thus formed. Carbon includesunwashed and acid-washed carbons. In some embodiments of this invention,suitable catalysts may be prepared by treating the carbon used ascatalyst support with acids such as HNO₃, HCl, HF, H₂SO₄, HClO₄,CH₃COOH, and combinations thereof. Acid treatment is typicallysufficient to provide carbon that contains less than 1000 ppm of ash.Some suitable acid treatments of carbon are described in U.S. Pat. No.5,136,113. In some embodiments of this invention, an activated carbon isdried at an elevated temperature and then is soaked for 8 to 24 hourswith occasional stirring in 1 to 12 weight percent of HNO₃. The soakingprocess can be conducted at temperatures ranging from room temperatureto 80° C. The activated carbon is then filtered and washed withdeionized water until the washings have a pH greater than 4.0 or untilthe pH of the washings does not change. Finally, the activated carbon isdried at an elevated temperature.

In some embodiments of this invention, carbon is an activated carbon. Insome embodiments of this invention, carbon is an acid washed activatedcarbon. The carbon can be in the form of powder, granules, or pellets,et al.

The effluent from the reaction zone typically includes residual startingmaterials R_(f)CHClCH₂Cl, desired hydrochlorofluoroolefin productR_(f)CCl═CH₂, dehydrochlorination byproduct R_(f)CH═CHCl and some otherbyproducts. The desired product R_(f)CCl═CH₂ may be recovered from theproduct mixture by conventional methods. In some embodiments of thisinvention, product R_(f)CCl═CH₂ may be purified or recovered bydistillation.

It was found through experiments that the catalytic dehydrochlorinationprocesses of this disclosure produced desired products with highselectivity. In some embodiments of this invention, the productselectivity to R_(f)CCl═CH₂ is at least 90 mole %. In some embodimentsof this invention, the product selectivity to R_(f)CCl═CH₂ is at least96 mole %.

It was also found through experiments that the dehydrochlorinationreaction of this disclosure is highly selective. The dehydrochlorinationreaction of R_(f)CHClCH₂Cl may generate both isomers R_(f)CCl═CH₂ andR_(f)CH═CHCl. It was found that the dehydrochlorination processes ofthis disclosure generate substantially more R_(f)CCl═CH₂ thanR_(f)CH═CHCl. In some embodiments of this invention, thedehydrochlorination selectivity to R_(f)CCl═CH₂ is at least 95 mole %.In some embodiments of this invention, the dehydrochlorinationselectivity to R_(f)CCl═CH₂ is at least 98 mole %.

The reactors, distillation columns, and their associated feed lines,effluent lines, and associated units used in applying the processes ofembodiments of this invention may be constructed of materials resistantto corrosion. Typical materials of construction include Teflon™ andglass.

Typical materials of construction also include stainless steels, inparticular of the austenitic type, the well-known high nickel alloys,such as Monel™ nickel-copper alloys, Hastelloy™ nickel-based alloys and,Inconel™ nickel-chromium alloys, and copper-clad steel.

Many aspects and embodiments have been described above and are merelyexemplary and not limiting. After reading this specification, skilledartisans appreciate that other aspects and embodiments are possiblewithout departing from the scope of the invention.

EXAMPLES

The concepts described herein will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

Example 1

Example 1 demonstrates that contacting HCFC-243db with KCl supported onacid washed Takeda™ carbon generates HCFO-1233xf.

Preparation of HNO₃ Washed Takeda™ Carbon

Takeda™ activated carbon with surface area ranging from about 1000 m²/gto about 1200 m²/g was soaked in 1 wt % HNO₃ aqueous solution at roomtemperature for 12 hours before being fully washed with deionized waterand dried at 120° C. for 12 hours. The HNO₃ washed Takeda™ carbon wasthen loaded with KCl and used below.

Dehydrochlorination Reaction

10 cc (cubic centimeter) of catalyst granules of 25 wt % KCl/acid washedTakeda™ carbon were loaded into a 0.43 inch I. D. Monel™ reactor tube toform a catalyst bed. Gaseous HCFC-243db was passed through the catalystbed at a rate of 1.1 g/hr together with 4.3 ml/min N₂.

The effluent from the reactor tube was analyzed by GC and GC-MS. Theconversion rate of the starting material HCFC-243db, the productselectivity to HCFO-1233xf and HCFO-1233zd, and the dehydrochlorinationselectivity to HCFO-1233xf were listed in the Table 1 below which showsboth good product selectivity and good dehydrochlorination selectivityto HCFO-1233xf.

TABLE 1 Dehydro- Product Product chlorination Conversion SelectivitySelectivity Selectivity Temp Mole % Mole % Mole % Mole % ° C. HCFC-243dbHCFO-1233xf HCFO-1233zd HCFO-1233xf 145 9.17 92.34 0.49 99.47 176 45.4798.64 0.74 99.26 176 53.66 98.83 0.81 99.19 202 89.83 98.61 1.18 98.82197 94.57 98.59 1.28 98.72 226 98.19 97.59 2.10 97.89 230 98.13 97.551.93 98.06 254 99.06 96.32 3.04 96.94 247 98.99 96.66 2.76 97.22 21798.48 97.55 2.01 97.98 224 98.13 98.05 1.74 98.26 222 98.20 98.07 1.7798.23

Example 2 (Comparative)

Example 2 demonstrates that the HCFC-243db conversion rate and theselectivity to HCFO-1233xf were low without a catalyst.

10cc Hastelloy™ 276 turnings were loaded into a 0.43 inch I. D. Monel™reactor tube to form a bed. Gaseous HCFC-243db was passed through thebed at a rate of 1.1 g/hr together with 4.3 ml/min N₂. The effluent fromthe reactor tube was analyzed by GC and GC-MS. The results are listed inthe Table 2 below.

TABLE 2 Dehydro- Product Product chlorination Conversion SelectivitySelectivity Selectivity Temp Mole % Mole % Mole % Mole % ° C. HCFC-243dbHCFO-1233xf HCFO-1233zd HCFO-1233xf 401 5.92 12.10 26.60 31.27 403 4.1619.79 48.45 29.00 429 13.06 24.66 64.97 27.51 423 12.82 25.23 66.7927.42 450 40.75 25.62 70.35 26.70 449 42.37 25.62 71.01 26.51 476 73.3524.53 68.81 26.28 471 74.01 25.18 70.71 26.26 500 84.00 22.17 60.9226.68 499 73.92 23.26 65.47 26.21

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that one or more further activitiesmay be performed in addition to those described. Still further, theorder in which activities are listed are not necessarily the order inwhich they are performed. In the foregoing specification, the conceptshave been described with reference to specific embodiments. However, oneof ordinary skill in the art appreciates that various modifications andchanges can be made without departing from the scope of the invention asset forth in the claims below. Accordingly, the specification is to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope ofinvention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

It is to be appreciated that certain features are, for clarity,described herein in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.

What is claimed is:
 1. A dehydrochlorination process comprisingcontacting R_(f)CHClCH₂Cl with a catalyst in a reaction zone to producea product mixture comprising R_(f)CCl═CH₂, wherein said catalystcomprises an alkali metal halide salt of the formula MY supported oncarbon, and wherein R_(f) is a perfluorniated alkyl group, M=K, Na orCs, and Y=F, Cl or Br and wherein the catalyst contains from about 5wt %to about 40wt % alkali metal halide salt based on the total amount ofalkali metal halide salt and carbon.
 2. The dehydrochlorination processof claim 1 wherein the carbon is an activated carbon.
 3. Thedehydrochlorination process of claim 2 wherein the carbon is an acidwashed activated carbon.
 4. The dehydrochlorination process of claim 1wherein M is K and Y is F or Cl.
 5. The dehydrochlorination process ofclaim 1 wherein the temperature in the reaction zone is from about 140°C. to about 400° C.
 6. The dehydrochlorination process of claim 5wherein the temperature in the reaction zone is from about 150° C. toabout 250° C.
 7. The dehydrochlorination process of claim 6 wherein thetemperature in the reaction zone is from about 175° C. to about 225° C.8. The dehydrochlorination process of claim 1 wherein the productselectivity to R_(f)CCl═CH₂ is at least 90 mole %.
 9. Thedehydrochlorination process of claim 1 wherein the product selectivityto R_(f)CCl═CH₂ is at least 96 mole %.
 10. The dehydrochlorinationprocess of claim 1 wherein the dehydrochlorination selectivity toR_(f)CCl═CH₂ is at least 95 mole %.
 11. The dehydrochlorination processof claim 1 wherein R_(f) is CF₃.
 12. The dehydrochlorination processaccording to claim 1 wherein the catalyst contains from about 10 wt % toabout 30 wt % alkali metal halide salt based on the total amount ofalkali metal halide salt and carbon.
 13. A dehydrochlorination processcomprising contacting R_(f)CHClCH₂Cl with a catalyst in a reaction zoneto produce a product mixture comprising R_(f)CCl═CH₂, wherein saidcatalyst comprises MY supported on carbon, and wherein R_(f) is aperfluorniated alkyl group, M=K, Na or Cs, and Y=F, Cl or Br, whereinthe product selectivity to R_(f)CCl═CH₂ is at least 90 mole %.
 14. Thedehydrochlorination process of claim 13 wherein the carbon is anactivated carbon.
 15. The dehydrochlorination process of claim 14wherein the carbon is an acid washed activated carbon.
 16. Thedehydrochlorination process of claim 13 wherein M is K and Y is F or Cl.17. The dehydrochlorination process of claim 13 wherein the temperaturein the reaction zone is from about 140° C. to about 400° C.
 18. Thedehydrochlorination process of claim 17 wherein the temperature in thereaction zone is from about 150° C. to about 250° C.
 19. Thedehydrochlorination process of claim 18 wherein the temperature in thereaction zone is from about 175° C. to about 225° C.
 20. Thedehydrochlorination process of claim 13 wherein the product selectivityto R_(f)CCl═CH₂ is at least 96 mole %.
 21. The dehydrochlorinationprocess of claim 13 wherein the dehydrochlorination selectivity toR_(f)CCl═CH₂ is at least 95 mole %.
 22. The dehydrochlorination processof claim 13 wherein R_(f) is CF₃.